Videoconference system and management method thereof

ABSTRACT

A videoconference system and a management method thereof are provided. The videoconference system includes: terminals; multipoint control units (MCUs), as the superior level for the terminals, for controlling the corresponding terminals; conference management systems, as the superior level for the MCUs, for performing dispatching and control for the local conference site; and conference coordination systems, as the superior level for the conference management systems, for coordinating corresponding conference management systems and neighboring conference coordination systems to perform dispatching and control for the entire conference. The videoconference management method includes: a subscriber requesting for conference dispatching to the home conference management system; the home conference management system managing the corresponding local conference site directly at the dispatching request, and transferring the dispatching across conference management systems to the corresponding conference coordination system; and the conference coordination system dispatching the corresponding master and slave conference management systems at the dispatching request.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/578,761, filed May 5, 2006, which is a national phase ofInternational Patent Application No. PCT/CN2004/001150, filed Oct. 11,2004, which claims the benefit of Chinese Patent Application No.200310113933.3, filed Nov. 5, 2003, all of which are hereby incorporatedby reference herein in their entireties.

FIELD OF THE INVENTION

The present invention relates to videoconference technology, moreparticularly to a videoconference system and a management methodthereof.

BACKGROUND OF THE INVENTION

In a videoconference, the participants can hear/see one party, multipleparties, or all other participants by encoding/decoding and transmissionof video and audio data. At present, videoconference systems mainlyinclude a narrow-band videoconference system that employs ITU-T H.320Series standard and a VoIP videoconference system that employs H.323Series standard. Referring to FIG. 1, a videoconference system mainlyincludes a Multipoint Control Unit (MCU) 1 and terminals 2. MCU 1 cancontrol multiple terminals in the videoconference. Since all video andaudio data has to be processed by MCU 1 (sometimes encoding/decoding isalso required). The access capability and data processing capability ofMCU 1 limit the maximum number of videoconferences supported as well asthe maximum number of terminals 2. Furthermore, compared with terminals2, MCU 1 is more expensive, and thereby is a precious resource invideoconference systems. Therefore, a conference management system isrequired to perform conference dispatching and allocation of MCUresource.

In general, traditional videoconference systems are oriented toenterprises and private network markets, and the conference managementsystem mainly pertains to either of the following two solutions:

The first solution: The MCU manufacturer provides a local conferencemanagement system 41 or a conference management system embedded in MCU 1for managing terminals 2, as shown in FIG. 2. In this solution, adedicated administrator has to be assigned for each MCU 1; thesubscribers request for conference dispatching to the administrator vianetwork 3 by telephone, fax, or email; the administrator performsdispatching for the corresponding conference in the videoconferencesystem in accordance with the requests from subscribers. If a cascadeconference has to be dispatched, the administrator has to determinewhich terminals 2 are under MCU 1 manually and create cascadedconference sites manually.

The second solution: if there are multiple MCUs 1, usually theconference is managed in a centralized manner, as shown in FIG. 3. Thatis to say, a dedicated conference management system 43 is used to managethe multiple MCUs 1. Such a videoconference system usually provides asubscription interface, through which the subscribers can request forconference dispatching; the conference management system 43 willaccomplish the allocation of MCU 1 resource and the cascadingautomatically.

SUMMARY OF THE INVENTION

An advantage of the present invention is to provide a videoconferencesystem and a management method thereof, so as to implement dispatchingand control of conference management systems across conferences.

A videoconference system according to the embodiment of the presentinvention includes: (1) terminals; (2) multipoint control units, as thesuperior level for the terminals, for controlling the correspondingterminals to participate in the videoconference; (3) conferencemanagement systems, as the superior level for the multipoint controlunits, for managing resource allocation of the corresponding subordinatemultipoint control units to meet subscribers' demand, and performingconference dispatching and control for the local conference site; and(4) conference coordination systems, as the superior level for theconference management systems, for coordinating correspondingsubordinate conference management systems and the neighboring conferencecoordination systems to perform dispatching and control for the entireconference at a dispatching request.

Each conference coordination system includes: (1) a system managementmodule, for accomplishing system configuration and operating managementof the conference coordination system; (2) a conference dispatchingmodule, for processing conference dispatching requests from thesubordinate conference management systems or from the neighboringconference coordination systems; (3) a conference control module, forforwarding conference control data; and (4) a multipoint communicationmodule, for communicating with the subordinate conference managementsystems and the neighboring conference coordination systems.

The multipoint communication data in the multipoint communication moduleincludes source node ID, channel ID, list of destination nodes, upperlayer application data and application data segment mark, and theconference coordination systems implement routing strategy by using thechannel ID and list of destination nodes in the multipoint communicationdata.

The system configuration of the system management module includes: (1)the terminals being numbered uniformly; (2) the conference managementsystem being configured with number segments to determine correspondingterminals; and (3) the conference coordination systems being configuredwith number segments managed by the corresponding conference managementsystems and number segments managed by the neighboring conferencecoordination systems, so as to determine a plurality of conferencemanagement systems involved in the conference in accordance with thesystem configuration, split the conference into sub-conferences, anddistribute the sub-conferences to each corresponding subordinateconference management system during a videoconference.

During a videoconference, the conference coordination systems determinea master conference management system and a slave conference managementsystem dynamically in accordance with the system configuration anddispatching strategy.

During a videoconference, one of the subordinate multipoint controlunits managed by the master conference management system serves as themaster multipoint control unit, the other multipoint control units inthe master conference management system and the multipoint control unitsin the slave conference management system serve as slave multipointcontrol units, and the master conference management system accomplishescascading among the master and slave multipoint control units.

The dispatching strategy of the conference coordination systems is todetermine the master conference management system in accordance with thenumber of terminals managed by the conference management systems and todetermine whether to merge the sub-conferences into the masterconference management system in accordance with the number ofsub-conferences.

The videoconference system management method according to an embodimentof this invention includes the steps of: (1) a subscriber requesting forconference dispatching from the home conference management system; (2)the home conference management system managing the corresponding localconference sites directly at the dispatching request, and transferringthe dispatching across conference management systems to thecorresponding conference coordination system; and (3) the conferencecoordination system dispatching the corresponding master and slaveconference management systems at the dispatching request.

The dispatching step further includes the steps of: (1) the conferencecoordination system determining each terminal's home conferencemanagement system; (2) the conference coordination system splitting thevideoconference into sub-conferences and distributing thesub-conferences to each corresponding conference management system; and(3) the conference coordination system determining a master conferencemanagement system and a plurality of slave conference managementsystems.

Before the step of requesting for conference dispatching, thevideoconference system management method further includes the steps of:(1) numbering the terminals in the videoconference uniformly; (2)configuring the conference management systems with number segments todetermine corresponding terminals; and (3) configuring the conferencecoordination systems with number segments managed by the correspondingconference managements system and number segments managed by theneighboring conference coordination systems, so that the conferencecoordination system can perform dispatching in accordance with thecorresponding managed number segments.

The videoconference system management method further includes thefollowing step between the step of managing and transferring of the homeconference management system and the dispatching step: the conferencecoordination system dispatching the corresponding neighboring conferencecoordination systems.

The videoconference system management method further includes thefollowing steps after the dispatching step: (1) the master and slaveconference management systems feeding the dispatching result back to thecorresponding conference coordination system; and (2) the conferencecoordination system feeding the final dispatching result back to thehome conference management system that sent the dispatching request.

Compared with the conventional art, the embodiments of this inventionhave the following advantages: (1) with a distributed and cascadedvideoconference management mechanism to implement dispatching across theentire network and the entire videoconference, and thus it can optimizethe operator's network configuration, improve equipment utilization, andreduce investment cost; (2) it can implement automatic cascading, holdany large-scale videoconference efficiently and quickly, without anyneed to designate a dedicated person to perform conference dispatchingand control, and thereby can easily implement interconnection acrossoperators and across countries to meet the demand for publicvideoconference operation; and (3) through conference dispatching bynumber segments and thresholds of terminals, it can make utilization ofMCU and network resources more rational.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the schematic diagram of a videoconference system;

FIG. 2 is the diagram of an embodiment of a conventional videoconferencesystem in the ;

FIG. 3 is the diagram of another embodiment of the conventionalvideoconference system in the ;

FIG. 4 is the diagram of a videoconference system according to a firstembodiment of the present invention;

FIG. 5 is the diagram of an embodiment of the solution as shown in FIG.4;

FIG. 6 is the block diagram of the conference coordination system in thevideoconference system according to the first embodiment of the presentinvention;

FIG. 7 is the diagram of the communication model of conferencecoordination system in the videoconference system according to the firstembodiment of the present invention;

FIG. 8 is the diagram of a videoconference system according to a secondembodiment of the present invention; and

FIG. 9 is the flow diagram of the method for managing thevideoconference system according to the second embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the videoconference system according to an embodiment of the presentinvention, a superior conference coordination system is added based onthe existing centralized conference management system, so that theisolated videoconference systems are integrated into a videoconferencenetwork, in order to take full advantage of the scale merit of thenetwork to meet the demand of the videoconference operation.

The videoconference system according to an embodiment of the presentinvention is in a tree-type distributed structure and includes:multipoint control units, terminals, conference management systems, andconference coordination systems; in which the terminals refer to networkdevices that can perform bidirectional and real time communication withthe multipoint control units or other terminals. The communicationincludes control, instructions, voice, moving images, and/or data.

The Multipoint Control Units (MCUs) serve as the superior level for theterminals and controls the corresponding subordinate terminals toparticipate in the videoconference.

The conference management systems serve as the superior level for theMCUs and are used to manage resource allocation of the correspondingsubordinate MCUs to meet subscribers' demand as well as performconference dispatching and control for the local conference sites (i.e.,terminals participating in the conference) during the conference.

The conference coordination systems serve as the superior level for theconference management systems, and are used to coordinate eachcorresponding subordinate conference management system and neighboringconference coordination systems to perform dispatching and control forthe entire conference at the dispatching request.

The conference coordination systems are superior to the conferencemanagement systems; each conference coordination system can managemultiple conference management systems; each conference managementsystem communicates with only the corresponding conference coordinationsystem. The conference coordination systems are peer to peer and canrequest for conference dispatching to each other.

Hereinafter, the dispatching request refers that a subscriber requestsfor conference dispatching (including start time, duration of theconference and terminals involved in the conference) from the homeconference management system, i.e., the conference management systemwhere the account number of the conference caller is.

The conference coordination systems perform control of the conferencewith conference control data which includes conference state data andconference control commands. Wherein, the conference state data refersto the data reported by each conference management system to thecorresponding superior conference coordination system and forwarded bythe conference coordination system to other conference managementsystems, including start/end of conference, entering/leaving ofconference site, or change of chairman token; the conference controlcommands include prolongation/ending of conference, calling/hangingup/adding/deleting/broadcasting/viewing of conference site, setting modeof continuous presence, etc. The conference coordination systems forwardconference state data and conference control commands to otherconference management systems participating in the videoconference, andrecord the original bill data for data verification in the settlementbetween the conference management systems.

In the embodiment as shown in FIG. 4, the conference coordinationsystems are disposed separately. In this case, the videoconferencesystem includes: (1) twenty-two terminals 2; (2) six MCUs 1, which serveas the superior level for terminals 2, and each MCU 1 manages twoterminals 2; (3) conference management systems 44, 45 and 46 serving asthe superior level for MCUs 1, each of the conference management systemsmanages two MCUs 1; and (4) conference coordination systems 51 and 52serving as the superior level for the conference management systems 44,45, and 46; wherein, the conference coordination system 51 is thesuperior level for the conference management systems 44 and 45, whilethe conference coordination system 52 is the superior level for theconference management system 46; the conference coordination systems 51and 52 are neighboring to each other, and can dispatch each other.

In order to enable the conference coordination systems to coordinateeach corresponding subordinate conference management system and theneighboring conference coordination systems to perform dispatching andcontrol of the entire conference in accordance with dispatchingrequests, conference control data and dispatching strategy, the entirevideoconference system is configured uniformly. The conferencecoordination systems need to determine each terminal's home conferencemanagement system. In this embodiment, the terminals are configuredsimilar to telephone numbers, as shown in FIG. 5:

The terminals in the videoconference system are configured with numbersuniformly (e.g., in E.164 code). For example, the twelve terminals areconfigured with numbers as follows: 07551001, 07551002, 0201001,0201002, 0101001, 0101002, 0102003, 0102004, 01231001, 01231002,01231003, and 01231004.

The conference management systems determine the correspondingsubordinate terminals in accordance with the configured number segments.In this embodiment, a number segment is used to serve as the commonprefix of the numbers of terminals corresponding to the conferencemanagement systems. For example, the conference management systems withthe configured number segments 0755 and 020 can manage terminals withnumber prefixes 0755 and 020, while the conference management systemswith the configured number segment 010 can manage terminals with numberprefix 010. Similarly, the conference management systems with theconfigured number segment 0123 can manage terminals with number prefix0123.

The conference coordination systems are configured with number segmentsmanaged by the corresponding conference management systems and numbersegments managed by the neighboring conference coordination systems. Forexample, the conference coordination systems with the configured numbersegments 0086755, 008620 and 008610 can manage the conference managementsystems with the configured number segments 0755, 020 and 010 andthereby determine terminals corresponding to the conference managementsystems, i.e., determine the conference management systems correspondingto the terminals that are numbered uniformly. Similarly, the conferencecoordination system with the configured number segment 001123 can managethe conference management systems with the configured number segment0123, and thereby determine the terminals corresponding to theconference management systems. The conference coordination systems thatcan dispatch each other are configured as “neighboring” conferencecoordination systems.

During a videoconference, a conference coordination system determinesmultiple conference management systems involved in the conference inaccordance with the system configuration (terminal number, numbersegment configuration, etc., wherein each terminal participating in theconference is also referred to as a conference site), and splits theconference into sub-conferences and distributes them to thecorresponding subordinate conference management systems (thevideoconference held by each conference management system is referred toas a sub-conference of the videoconference), and determines a masterconference management system and slave conference management systemsdynamically in accordance with dispatching strategy. Hereinafter theconference coordination systems are described in detail with referenceto the dispatching process:

The conference coordination systems determine the conference managementsystems or the conference coordination systems corresponding to theterminals in accordance with the terminal numbers, so as to determinethe conference management systems involved in the conference. Theconference coordination systems split the conference into multiplesub-conferences and then distribute them to other conference managementsystems.

The conference coordination systems determine the master conferencemanagement system in accordance with the corresponding strategy; forexample, the conference coordination systems can determine the masterconference management system (i.e., the conference management systemwhere the master MCU is; hereinafter the master conference managementsystem will be described in detail) in accordance with the number ofterminals.

The conference coordination systems determine whether to mergesub-conferences in accordance with appropriate dispatching strategy, soas to reduce unnecessary cascades; for example, a threshold may be set,so that the terminals involved in the sub-conferences can be merged intothe master conference management system directly when the number ofsub-conference sites is lower than the threshold. Here, the dispatchingstrategy of the conference coordination systems is to determine themaster conference management system in accordance with the number ofterminals managed by the conference management systems and to determinewhether to merge the sub-conferences into the master conferencemanagement system in accordance with the number of sub-conferences.

In addition, the master conference management system refers to theconference management system where the master MCU is when a cascadeacross conference management systems is required in a videoconference.The slave conference management systems refer to conference managementsystems that do not contain the master MCU when cascades acrossconference management systems are required in a videoconference. In thesubordinate MCUs managed by the master conference management system,only one MCU serves as the master MCU, while the other MCUs managed bythe master conference management system and the MCUs managed by theslave conference management systems serve as slave MCUs, and the masterconference management system accomplishes cascading among the master andslave MCUs. In addition, “cascade” here refers to the conference mode ofthe master and slave MCUs cascading with each other in avideoconference, i.e., a videoconference is held based on multiple MCUs,wherein there is only one master MCU, and the other MCUs are slave MCUs;the master and slave MCUs are linked together directly throughcommunication link connections.

During conference dispatching, when a conference management systemreceives conference dispatching request data, it treats the localconference site independently first (the number segment managed by eachconference management system can be configured and distributed to eachcorresponding conference management system by a conference coordinationsystem). If all of the conference sites are local ones, the conferencemanagement system will dispatch locally and doesn't need to interactwith the conference coordination systems.

If the conference involves any conference site that does not correspondto the conference management system, the conference management systemwill submit the dispatching request to a conference coordination systemfor processing. The conference coordination system will send asub-conference dispatching request to each corresponding conferencemanagement system or the conference coordination system (more details inthe dispatching process of the conference coordination system). Afterall sub-conferences are dispatched successfully, the master conferencemanagement system will accomplish the cascading among the master andslave MCUs.

During a conference across multiple conference management systems, sinceeach conference management system can only manage and control the stateof the sub-conference held in itself, the conference coordination systemhas to route and transfer conference state data and control commands tocontrol the entire conference and manage allocation of MCU resource, soas to ensure the resource required by the conference meet thesubscribers' requirements. A conference across systems can beimplemented by the conference management systems communicating with theconference coordination systems. When the conference management systemdoes not communicate with the conference coordination system, itoperates as a centralized conference management system.

In particular, each conference coordination system includes (See FIG.6): (1) a system management module 61, for accomplishing systemconfiguration (e.g., numbering, number segment configuration) andoperating management of the conference coordination system; (2) aconference dispatching module 62, for processing conference dispatchingrequests from the subordinate conference management systems or theneighboring conference coordination systems; (3) a conference controlmodule 63, for forwarding conference control data; and (4) a multipointcommunication module 64, for communicating with the subordinateconference management systems and the neighboring conferencecoordination systems.

As shown in FIG.7, the communication models between a conferencecoordination systems and the subordinate conference management systemsas well as between the conference coordination systems are based on theInternational Organization for Standardization (ISO) 7-layer model forcommunication; wherein, the International Telecommunications Uniontransport service ITU-T X.224 is used below transport layer 71, theupper layer for the transport layer 71 is a multipoint communicationmodule 64. The upper layer for the multipoint communication module 64 isa conference management application layer 72 (e.g., a conferencedispatching module 62, a conference control module 63).

The multipoint communication data in the multipoint communication module64 employs (but not limited to) the following format to carry upperlayer data:

{   source node ID,   channel ID,   list of destination nodes;  application data segment mark,   upper layer application data,   ... }

Each conference coordination system implements routing strategy byutilizing the channel ID and list of destination nodes in the multipointcommunication data, so as to improve communication efficiency andfacilitate modular design of upper layer applications. For example,channels with IDs of 1-1,000 can be used to transfer conferencedispatching request data; channels with ID>1,000 can be used to controlthe conference. The conference dispatching request data can be sentdirectly to the conference dispatching module 62 for processing. Forconference control data (including state data and control commands), therouting strategy can be configured further. For example, when theconference coordination systems do not need the conference controlfunction, it is unnecessary to send the conference control data to theconference control module 63 in each conference coordination system.When the conference coordination systems need only billing function, theconference control module 63 can send only start/end of conference,entering/leaving of conference site etc., and billing-relevantinformation to the conference coordination systems; when a conferencemanagement system doesn't need to control the conference, it isunnecessary to send the conference control data to the conferencemanagement system. That is to say, the conference coordination systemsperform conference control as required, besides conference dispatchingacross systems.

The conference coordination systems may be separated from the conferencemanagement systems (see FIG. 4 and FIG. 5) or embedded in thecorresponding conference management systems (see FIG. 8).

Accordingly, the method for managing the videoconference systemcomprises the steps of: (1) a subscriber requesting for conferencedispatching from the home conference management system; (2) the homeconference management system processing the corresponding localconference sites directly at the dispatching request, and transferringthe dispatching across conference management systems to thecorresponding conference coordination system; (3) the conferencecoordination system dispatching the corresponding master and slaveconference management systems at a dispatching request (during theconference dispatching process, the conference coordination systemperforming control of the conference in accordance with the conferencecontrol data and performing dispatching with reference to thedispatching strategy) by the steps of: (a) the conference coordinationsystem determining each terminal's conference management system; (b) theconference coordination system splitting the videoconference intosub-conferences and distributing them to the corresponding conferencemanagement systems; (c) the conference coordination system determiningthe master conference management system and the slave conferencemanagement systems; (d) the master and slave conference managementsystems feeding the dispatching result back to the correspondingconference coordination system; and (e)the conference coordinationsystem feeding the final dispatching result back to the home conferencemanagement system that sent the dispatching request.

If the dispatching request indicates to dispatch a neighboringconference coordination system, dispatching a corresponding neighboringconference coordination system in accordance with the correspondingnumber segment managed by it; the corresponding conference coordinationsystem executing the dispatching step to the step of feeding thedispatching result.

Before the dispatching process, the videoconference system managementmethod includes the steps of: (1) numbering terminals in thevideoconference system uniformly; (2) the conference management systemsdetermining corresponding terminals in accordance with the configurednumber segments; and (3) configuring the conference coordination systemswith number segments managed by the corresponding conference managementsystems and number segments managed by the neighboring conferencecoordination systems.

FIG. 9 shows an embodiment of the method for managing thevideoconference system. When a cascaded conference site is added acrossconference management systems, the method includes the following steps:(1) a subscriber requesting for conference dispatching to the homeconference management system; (2) determining whether the conferencedispatching request is a request across conference management systems ora local request; (3) the home conference management system processingthe request, i.e., if the request is a local request, processing thecorresponding local conference site; otherwise, transferring thedispatching across conference management systems to the correspondingconference coordination system; (4) the conference coordination systemdispatching the corresponding master and slave conference managementsystems by the managed corresponding number segments in accordance withthe dispatching request, conference control data, and dispatchingstrategy; (5) the master and slave conference management systems feedingthe dispatching result back to the conference coordination system;wherein (a) the corresponding conference coordination system dispatchingthe master conference management system; (b) the master conferencemanagement system feeding the dispatching result back to the conferencecoordination system; (c) the conference coordination system dispatchingthe slave conference management systems in accordance with thedispatching result; (d) the slave conference management systems feedingthe dispatching result back to the conference coordination system; (e)the conference coordination system dispatching the master conferencemanagement system to add a cascaded conference site; (f) the masterconference management system feeding the cascading result back to theconference coordination system; and (g) the conference coordinationsystem feeding the final dispatching result back to the home conferencemanagement system that sent the dispatching request.

If the dispatching request indicates to dispatch a neighboringconference coordination system, dispatching a corresponding neighboringconference coordination system is dispatched in accordance with thecorresponding number segment managed by it; the corresponding conferencecoordination system executing corresponding dispatching process.

During a videoconference, the process of adding a terminal or prolongingthe videoconference is similar to the process of adding a cascadedconference site across conference management systems, which will not bedescribed in further detail.

In conclusion, compared with the conventional art, the videoconferencesystem and the management method thereof according to the embodiments ofthe present invention employ a cascaded and distributed conferencemanagement to implement dispatching for the entire conference across theentire network, and thereby optimize the operator's networkconfiguration, improve equipment utilization, and reduce investmentcost; in addition, the videoconference system and the management methodthereof can implement automatic cascading and hold any large-scalevideoconference efficiently and quickly, without any need to designate adedicated person to perform conference dispatching and control, therebycan easily implement networking across operators and across countries tomeet the demand for public videoconference operation; through conferencedispatching by number segments and thresholds of terminals, thevideoconference system and the management method thereof can makeutilization of MCU and network resources more logical.

1. A videoconference system, comprising: terminals; multipoint control units (MCUs), as a superior level for the terminals, for controlling the corresponding terminals to participate in a videoconference; conference management systems, as a superior level for the MCUs, for managing resource allocation of the corresponding MCUs, and performing conference dispatching and control for a local conference site; and conference coordination systems, as a superior level for the conference management systems, for determining multiple conference management systems involved in the conference in accordance with the system configuration, splitting the conference into sub-conferences, and distributing them to the corresponding subordinate conference management systems.
 2. The videoconference system according to claim 1, wherein after distributing them to the corresponding subordinate conference management systems, the conference coordination system determines a master conference management system and slave conference management systems dynamically in accordance with dispatching strategy.
 3. The videoconference system according to claim 2, wherein determining multiple conference management systems involved in the conference in accordance with the system configuration, splitting the conference into sub-conferences, distributing them to the corresponding subordinate conference management systems comprises: determining, by the conference coordination systems, the conference management systems or the conference coordination systems corresponding to the terminals in accordance with the terminal numbers; splitting the conference into multiple sub-conferences and then distributing them to other conference management systems; wherein determining a master conference management system and slave conference management systems dynamically in accordance with dispatching strategy comprises: determining, by the conference coordination systems, the master conference management system in accordance with the corresponding strategy; and then determining whether to merge sub-conferences in accordance with appropriate dispatching strategy so as to reduce unnecessary cascades.
 4. The videoconference system according to claim 2, wherein at least one of the following below information is adapted to determine multiple conference management systems involved in the conference in accordance with the system configuration, to split the conference into sub-conferences, and to distribute them to the corresponding subordinate conference management systems: the terminals being numbered uniformly; the conference management system being configured with number segments to determine corresponding terminals; and the conference coordination systems being configured with the number segments managed by the corresponding conference management systems and number segments managed by the neighboring conference coordination system.
 5. The videoconference system according to claim 2, wherein the dispatching strategy of the conference coordination systems is to determine the master conference management system in accordance with the number of terminals managed by the conference management systems and to determine whether to merge the sub-conferences into the master conference management system in accordance with the number of the sub-conferences.
 6. The videoconference system according to claim 2, wherein the conference coordination systems are separated from or embedded in the conference management systems.
 7. A videoconference system management method, comprising the steps of: subscribing requesting for conference dispatching from home conference management systems; managing, by the home conference management systems, the corresponding local conference site directly in response to the dispatching request, or transferring the dispatching across conference management systems to a corresponding conference coordination system; and implementing, by the conference coordination system as a superior level for the conference management systems, the coordinating step: determining multiple conference management systems involved in the conference in accordance with the system configuration, splitting the conference into sub-conferences, and distributing them to the corresponding subordinate conference management systems.
 8. The videoconference system management method according to claim 7, wherein the coordinating step further comprises: determining, by the conference coordination system, a master conference management system and slave conference management systems dynamically in accordance with dispatching strategy.
 9. The videoconference system management method according to claim 8, wherein before the step of requesting for conference dispatching, the method further comprises the following steps: numbering terminals in the videoconference uniformly; configuring the conference management systems with number segments to determine corresponding terminals; and configuring the conference coordination system with the number segments managed by the corresponding conference management systems and number segments managed by the neighboring conference coordination system, so that the conference coordination system can perform dispatching in accordance with the corresponding managed number segments.
 10. The videoconference system management method according to claim 8, wherein after the coordinating step, the method further comprising the following steps: feeding, by the master and slave conference management systems, a coordinating result back to the corresponding conference coordination systems; feeding, by the conference coordination systems one or more final coordinating results back to the home conference management systems that send the dispatching requests.
 11. The videoconference system management method according to claim 8, wherein after the coordinating step, the conference coordination systems perform conference dispatching with reference to a dispatching strategy, and the dispatching strategy is: to determine the master conference management system in accordance with the number of terminals managed by each conference management system and determine whether to merge the sub-conferences into the master conference management system in accordance with the number of the sub-conferences.
 12. The videoconference system management method according to claim 8, wherein the dispatching request refers to that the subscriber requests for conference dispatching from the conference management system where the account number of a conference caller is, including a start time, a duration of the conference and terminals involved in the conference. 